The present invention relates to a reduction apparatus, and more particularly, the present invention relates to a reduction apparatus which can be applied to power transmission systems for a variety of machines and which uses planetary gears to reduce a rotational velocity of an output shaft in the course of transferring a rotational velocity of an input shaft to the output shaft, thereby enabling a large and highly precise reduction ratio to be obtained.
Generally, various machine tools or industrial machines are equipped with a reduction apparatus which serves to change a driving RPM generated by and transferred from a power source to other RPMs suitable for operating them. The reduction apparatus must be provided with a separate reverse rotation preventing device for braking a reverse load which is transferred to an input shaft from an output shaft when a power source is shut off.
However, the conventional reduction apparatus suffers from defects in that a combination of spur gears, warm gears and the like, is used, a kinetic mechanism is involved. Also, since the whole load acts on only a single tooth, one at a time when gears are meshed one with another, each tooth is apt to be abraded whereby durability and operation reliability of the reduction apparatus are deteriorated. Further, because the reverse rotation preventing device must be provided, the number of components is increased.
To resolve these defects, a reduction apparatus having a reverse rotating preventing function which is described in Korean Patent Application No. 98-19936 filed on May 29, 1998, had been disclosed in the art by the present applicant.
In the reduction apparatus having a reverse rotating preventing function, if power is applied to an input shaft 60 from driving means, a carrier 40 which is integrally formed with the input shaft 60, is rotated, and a double planetary gears 50 which are disposed in a receiving room 46 defined in the carrier 40, rotates about their own axes. The double planetary gear 50 also revolves due to the fact that a first planetary gear part 52 of the double planetary gear 50 is meshed with a fixed ring gear 20. At the same time, by the fact that a second planetary gear part 54 of the double planetary gear 50 is meshed with an output ring gear 34, an output member 30 including an output shaft 32 is rotated. At this time, a rotational velocity of the input shaft 60 which is rotated by the driving means (not shown), is reduced by a difference in the number of teeth or the module between the first and second planetary gear parts 52 and 54 or between the fixed ring gear 20 and the output ring gear 34, by which the reduced rotational velocity represents a rotational velocity of the output shaft 32.
Also, if no load is transferred to the input shaft 60 from the driving means, force for rotating the input shaft 60 in a reverse direction is generated due to a reverse load produced by the output shaft 32. At this time, even though the reverse load is transferred to the second planetary gear part 54 of the double planetary gear 50 through the output ring gear 34 of the output member 30, since the first planetary gear part 52 of the double planetary gear 50 having the number of teeth or the module which is different from that of the second planetary gear part 52, is meshed with the fixed ring gear 20, the reverse load is braked not to be transferred to the input shaft 60, whereby it is possible to perform a reverse rotation preventing function.
However, the conventional reduction apparatus having the reverse rotation preventing function is still encountered with a problem in that, since a reduction ratio is determined by a difference in the numbers of teeth of the first and second planetary gear parts 52 and 54 of the double planetary gear 50, a maximum reduction ratio which can be obtained with the conventional reduction apparatus, is a reduction ratio which is achieved when the number of second planetary gear part 54 is smaller by 1 than the number of first planetary gear part 52, whereby a limitation is imposed upon realizing a large and highly precise reduction ratio.
In other words, in the convention reduction apparatus, because the first and second planetary gear parts 52 and 54 have the same rotating shaft, distances from a center line of the input line 60 to center lines of the first and second planetary gear parts 52 and 54 are the same, in the case that modules which are formed in the first and second planetary gear parts 52 and 54, are differentiated from each other, the first and second planetary gears 52 and 54 cannot be adequately arranged, whereby a highly precise reduction ratio which is obtained by differentiating modules of the gears, cannot be realized.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a reduction apparatus using planetary gears, in which a separate rotating shaft is provided for each of the planetary gears, thereby to accomplish a large and highly precise reduction ratio.
In order to achieve the above object, according to the present invention, there is provided a reduction apparatus comprising: a cylindrical case having a pair of case parts which are detachably assembled with each other to define a receiving space; a fixed ring gear sandwiched between and coupled to the pair of case parts and having teeth which are formed on a circumferential inner surface thereof; an output member rotatably received in the receiving space of the case and having an output ring gear and an output shaft, the output ring gear being formed on a circumferential inner surface of the output member in a manner such that the output ring gear has an inner diameter which is the same as that of the fixed ring gear and a gear ratio and a module which are respectively different from those of the fixed ring gear, the output shaft being integrally formed on an outer surface of the output member to project out of the case; a carrier having a first carrier member and a second carrier member, the first carrier member possessing a circular plate-shaped configuration and having a guide projection and an input shaft-guiding groove, the guide projection being formed at a center portion of an outer surface of the first carrier member to be rotatably supported on an inner surface of the output member, the input shaft-guiding groove being defined at a center portion of an inner surface of the first carrier member, the second carrier member being arranged to be opposite to the first carrier member with a predetermined separation and to define an accommodating space between the first and second carrier members, the second carrier member having an input shaft-inserting hole which is defined at a center portion thereof; an input shaft having a shaft portion which is rotatably supported at one end thereof in the input shaft-guiding groove of the first carrier member and projects at the other end thereof out of the case through the input shaft-inserting hole of the second carrier member, the input shaft further having a first sun gear and a second sun gear which are formed on a circumferential outer surface of the shaft portion in a manner such that the first and second sun gears are located between the first and second carrier members and a gap is defined therebetween; a plurality of first planetary gears rotatably fitted around a plurality of first connecting members, respectively, which are secured to the first and second carrier members in a manner such that the first connecting members are spaced apart one from another by a predetermined angle along a circumferential direction, the first planetary gears being meshed with the first sun gear of the input shaft; and a plurality of second planetary gears rotatably fitted around a plurality of second connecting members, respectively, which are secured to the first and second carrier members in a manner such that each second connecting member is positioned between two first planetary gears in the circumferential direction, the second planetary gears being meshed with the second sun gear of the input shaft.